Effects of Doping on Conduction/Densification of BaCe0.5fZr0.3Y0.2O3-Δ Electrolyte for Green Hydrogen Applications

Abstract

For reaching the goal of 2050 net-zero carbon emission, the production of green H2 needs a very efficient and cost-effective approach. A proton-solid oxide electrolyzer cell (P-SOEC) based on BaCe0.5Zr0.3Y0.2O3-δ (BCZY) proton conducting electrolyte may show some advantages such as (1) Use of lower cost metals, alloys and coatings, (3) Ease of gas sealing, (4) Reduced cost of hydrogen production. BaCe0.5Zr0.3Y0.2O3-δ (BCZY) is known for its unique stability and high proton conduction properties due to the doping effect from the substitution of Zr and Y for Ce ions. For better performance of P-SOEC, a solid electrolyte with good densification to prevent the direct mixing of fuel and oxidant is essential.Thus, the objective of this study is to develop a cost-effective process with proper dopant in order to obtain well-densified BCZY at a temperature as low as 1200°C. For undoped BCZY, much less densification was observed. With the addition of proper dopant, BCZY may reach 97% relative density at the same temperature. It is believed that the presence of liquid phase is the reason for densification enhancement of doped BCZY. The affected electrical and structural properties will be analyzed and discussed based on sintering theory and kinetics. The crystal structure and microstructure of sintered BCZY was also characterized using XRD, field-emission SEM, and STEM.